1. Field of the Invention
This invention relates to flame-retardant polyethylene terephthalate resin compositions and, more particularly, to a flame-retardant glass-fiber-reinforced polyethylene terephthalate resin composition having a high degree of crystallizability.
2. Description of the Prior Art
Polyethylene terephthalate resins reinforced with glass fibers are known to have excellent mechanical properties and chemical resistance.
Accordingly, they are being used in the manufacture of heating appliance parts as well as electric and electronic parts. Among others, glass-fiber-reinforced polyethylene terephthalate resins having flame retardancy are especially suitable for use in electric and electronic parts.
However, conventional glass-fiber-reinforced polyethylene terephthalate resins have been disadvantageous in that, because of their low crystallization velocity, molded articles which have been crystallized to the fullest extent cannot be obtained unless high-temperature molds are used. Since the use of low-temperature molds does not permit an adequate degree of crystallization, the resultant resin moldings exhibit poor moldability and undergo marked shrinkage or warpage during after-heating.
In fields involving the use of small-sized, thin-walled articles such as electric and electronic parts, high-cycle molding with low-temperature molds is required to shorten the molding cycle, and dimensional stability is strongly desired for the resultant molded articles. In these fields, therefore, glass-fiber-reinforced polyethylene terephthalate resins having poorer high-cycle moldability and dimensional stability are being used in much smaller amounts, as compared with polybutylene phthalate resins that are analogous polyester resins. Thus, it would be desirable to improve the crystallizability of glass-fiber-reinforced polyethylene terephthalate resins.
In order to overcome the above-described disadvantages, the present inventor has made an intensive study and has found that a glass-fiber-reinforced polyethylene terephthalate resin having incorporated therein specified amounts of a polymeric flame retarder having a specific chemical structure and a certain compound effective in the promotion of crystallization can achieve an adequate degree of crystallization even at a mold temperature of 100.degree. C. or less and, therefore, can exhibit excellent moldability.